The present application relates to an optical element having an anti-reflection function, a method for producing the same, and a display apparatus including the same. More specifically, the present invention relates to an optical element in which a large number of structures, each of which is composed of a projection or a recess, are arranged on a surface at a fine pitch equal to or less than the wavelength of visible light, and a method for producing the same.
Some existing optical elements including a light-transmissive substrate composed of glass or plastic are subjected to a surface treatment for suppressing surface reflection of light. An example of such a surface treatment is to form fine and dense irregularities (moth eyes) on a surface of an optical element (refer to, for example, “Optical and Electro-Optical Engineering Contact”, Vol. 43, No. 11 (2005), pp. 630-637).
In general, when a periodically irregular shape is provided on a surface of an optical element and light is transmitted through the surface, diffraction occurs and rectilinear components of the transmitted light significantly decrease. However, when the pitch of the irregular shape is shorter than the wavelength of light to be transmitted, diffraction does not occur. For example, when the irregular shape is a rectangle described below, it is possible to achieve an anti-reflection effect for light having a single wavelength corresponding to the pitch or the depth of the irregular shape.
A moth-eye structure having a fine tent shape (pitch: about 300 nm, depth: about 400 nm) is disclosed as a moth-eye structure prepared by using an electron beam exposure technique (refer to, for example, NTT Advanced Technology Corporation, “Master mold for forming anti-reflective structure (moth eye) independent from wavelength”, [online], [searched on Feb. 27, 2008], Internet <http://keytech.ntt-at.co.jp/nano/prd_0033.html>). In this moth-eye structure, a high-performance anti-reflection characteristic of a reflectivity of 1% or less can be obtained.
In addition, hanging bell-shaped and truncated elliptical cone-shaped moth-eye structures are disclosed as moth-eye structures prepared by a method in which a process for preparing a master of an optical disk and an etching process are combined (refer to, for example, PCT International Publication No. 08/023816 Pamphlet). In these structures, anti-reflection characteristics close to those of the moth-eye structure prepared by the electron beam exposure technique are obtained.